HMO Planning and Licensing: What London Landlords Need to Know

If you own a property in London and you're thinking about converting it into a House in Multiple Occupation — or you already have one — the regulatory landscape is more layered than many landlords expect. Planning, licensing, and management obligations all operate in parallel, and getting any one of them wrong can expose you to financial penalties, enforcement action, or complications when you come to remortgage or sell.

This post sets out the key framework so you can approach an HMO project with a clear picture of what's involved.

C4 vs Sui Generis: The Planning Use Classes That Matter

Under the Town and Country Planning (Use Classes) Order 1987 (as amended), most standard residential homes sit in use class C3 (dwelling house). When a property is occupied by between three and six unrelated people forming more than one household, it falls into use class C4 — a small HMO.

When the number of unrelated occupants reaches seven or more, the property moves outside the use class system entirely and becomes what's known as sui generis — in a class of its own. This matters because permitted development rights (which allow certain changes of use without a full planning application) do not apply to sui generis uses. Converting a property to a larger HMO of seven or more occupants will always require full planning permission.

For the C3 to C4 transition — a smaller HMO of up to six people — there is a permitted development right in England that would ordinarily allow the change without a planning application. However, in London this right has been significantly eroded.

The Article 4 Direction: A Critical London Caveat

Many London boroughs have introduced Article 4 Directions that remove the permitted development right to convert from C3 to C4. This means that in those areas, even a small HMO of three to six unrelated people requires a full planning application.

Boroughs that have Article 4 Directions covering HMO conversions include — but are not limited to — Southwark, Tower Hamlets, Westminster, Hackney, Haringey, Lambeth, Lewisham, Waltham Forest, and Newham. Coverage varies and the picture can change, so it is essential to confirm the current position with the relevant local planning authority before assuming permitted development applies.

Where an Article 4 Direction is in place and you proceed without planning permission, you will be in breach of planning control — a position that can trigger enforcement action and will need to be resolved before any sale or refinancing.

It is also worth noting that converting a house into self-contained flats is a separate process altogether. Under section 257 of the Town and Country Planning Act 1990, this constitutes a material change of use and requires planning permission regardless of location — it is not covered by the HMO use class framework.

HMO Licensing: Three Tiers

Planning permission (or permitted development) establishes the lawfulness of the use. Licensing is a separate requirement under the Housing Act 2004 (as amended), and it operates in parallel.

Mandatory licensing applies nationally to any HMO occupied by five or more persons forming two or more households, spread across two or more storeys. This scope was extended in October 2018, bringing a wider range of properties into the mandatory scheme. A mandatory licence must be obtained from the local housing authority before the property is occupied as an HMO at this scale.

Beyond mandatory licensing, local authorities have discretion to introduce two further layers:

Additional licensing allows a council to extend licensing requirements to HMOs that fall below the mandatory threshold — for example, smaller properties with three or four occupants. Many London boroughs have introduced additional licensing schemes covering their entire borough or specific wards.

Selective licensing applies to all privately rented properties in a designated area, regardless of whether they are HMOs. This is typically introduced in areas the council has identified as having significant issues with low housing demand, anti-social behaviour, or poor property conditions.

You will need to check what schemes are in force in your specific borough, as the picture varies considerably across London.

The HMO Management Regulations

Holding a licence is not the end of it. The HMO Management Regulations 2006 (SI 2006/372) impose ongoing duties on the person managing the property. These include maintaining and repairing common areas and shared facilities, ensuring adequate fire precautions are in place, keeping gas and electrical installations in safe working order, and providing adequate refuse facilities.

In practical terms, this means your conversion needs to be designed and built with these obligations in mind from the outset. A fire risk assessment is a legal requirement. Interlinked smoke and heat detection alarms are expected — the precise requirements depend on the property type and the licensing conditions. Emergency lighting to escape routes is commonly required for larger HMOs. Means of escape must be adequate and kept free from obstruction.

Room sizes also carry a legal minimum. The Licensing of Houses in Multiple Occupation (Prescribed Description) (England) Regulations 2018 (SI 2018/221) set a minimum floor area of 6.51 square metres for a room occupied by a single adult. Rooms below the minimum cannot be let.

How RCB Design & Build Can Help

HMO conversions involve structural work, fire-stopping, thermal insulation upgrades, electrical rewiring, bathroom additions, and careful attention to escape routes — all of which require proper coordination with Building Control and a structural engineer where load-bearing work is involved.

At RCB Design & Build, we support landlords and investors through the full construction and compliance process for HMO conversions across London. We work alongside your planning consultant and licensing officer to make sure the building works deliver a finished property that is fit for licensing, safe for occupants, and built to a standard that will stand up to inspection.